1. Field of the Invention
The present invention relates to a structure of 3D inverted F-antenna, and more particularly to a structure of 3D inverted F-antenna, which is set into an electric device.
2. Description of the Prior Art
As communication technology has become more and more advanced, the related products are varied with its increasing applications in all fields. Besides, many kinds of communication products with different designs and functions are proposed due to the requests of the customers. For example, the PC networking products are currently popular as a result of convenience of wireless communication. In addition, as the technology of the integrated circuit (IC) is developed, the designs of communication devices tend to be compact size and light weight.
It is important to study and design the antenna, which is one of the components in the communication product for transmitting and receiving signals. Normally, we can realize the characteristics of the antenna by the parameters of Operating Frequency, Radiation Pattern, Return Loss, and Antenna Gain of the antenna.
Conventionally, the type of the antenna is primary a coil which is a roll of metal wire. The predetermined functions will be affected by the diameter, material, pitch, and the length of the helix antenna. However, as the antenna is protruding and external, the dimension of the product is increased and can't fit the requested designs of compact size and light weight.
Thus, tiny or planar microstrip antenna is invented to achieve above-mentioned requests. In the early years, the microstrip antenna comprises a circle or a rectangular thin metal sheet, as disclosed in the U.S. Pat. Nos. 3,921,177 and 3,810,183, and then dielectric is filled into the space between said thin metal sheet and the ground. Typically, the microstrip antenna works under narrow bandwidth. As to the polygonal helical microstrip antenna for improving the early microstrip antenna as described in the U.S. application number of Ser. No. 07/695,686, its bandwidth is closed to that of general helical antenna with constant impedance. But the disadvantage is that the diameter of the antenna will increase when it works at the low frequency. It cannot be carried in a pocket, either.
Recently, the most common used antenna such as Planer Inverted F-Antenna (PIFA) is a continuation of the conventional Inverted F-Antenna. The characteristics of PIFA are compact size, simple in structure, and easy to design, it is applied to many kinds of communication products or systems thereby.
The structure of the conventional inverted F-antenna 1 is described with reference to FIG. 1. A metal wire 11 is connected to the ground plate 10. And a short point 12 is connected to one terminal of the metal wire 11. Besides, a feed point 13 for connecting to a coax feed 14 is adjacent to the short point 12. Therefore, a single frequency antenna is formed.
The conventional inverted F-antenna can be developed to the Planer Inverted F-Antenna (PIFA) 2 as shown in FIG. 2. The PIFA 2 comprises a ground plate 20, a radiating plate 21, a short plate 22, a conductive signal feeding device 23, and a media 24 being between and isolating the ground plate 20 and the radiating plate 21. The media can be air, Styrofoam, microwave substrate, or the combination. Besides, the two ends of the short plate 22 are welded to the ground plate 20 and the radiating plate 21, respectively. The conductive signal feeding device 23 is in the ground plate 20 and coupled to the radiating plate 21 for transmitting signals. Further, the conductive signal feeding device 23 can be a TEM wire including an inner conductor 231 and an outer conductor 232 which are welded to the radiating plate 21 and the ground plate 20, respectively. While it works, the length of the antenna can be reduced to ¼ of the resonance wavelength due to the structure of the antenna.
However, when the PIFA as mentioned above is placed in some communication products such as a cellular phone or a notebook, good signal transmitting and receiving cannot often be provided. Furthermore, it is not convenient to manufacture and maintain the antenna due to the accuracy of the high welding technologies. Thus, for the manufacturer, the terms of high performance, low cost, and simple to manufacture cannot be achieved.